Scanning electron microscopes (SEM) are used in many applications in the evaluation of electronic, biological, and other types of samples. In SEM, a scanned electron beam interacts with a specimen to generate signals based on reflected, scattered, or transmitted electrons that can be used to produce specimen images. High-resolution images require scanning at many different specimen locations, and image acquisition can be slow. In some cases, specimens acquire charge upon exposure to the scanned electron beam, reducing image quality. While SEM operators can adjust scan times and beam currents to avoid specimen charging, such adjustments are subjective, slow, and require a skilled operator. In some cases, SEM operators evaluate images at selected areas at low resolution, and then adjust beam currents and dwell times accordingly. Unfortunately, these settings frequently do not produce the desired image quality. Accordingly, alternative methods and apparatus are needed to reduce charging effects in charged particle beam imaging.